Challenge the deadline
There are basically two kinds of deadlines: Real, and Arbitrary.
Real deadlines are those necessitated by some external, unchangeable event. For example legislation, the company running out of money, the CEO having to get up in front of the world press and announce the product, or a marketing campaign kicking off.
And then there are the much more common deadlines; The Arbitrary Deadline. They are recognizable by their basis in nothing at all - other than a decision that it would be nice to have X done by this or that date.
They are often employed in a naive attempt to speed up production. The thinking seems to be "give the wizkids a tight deadline, and they'll really dig in and program the heck out of this".
Deadlines don't change anything
But here's the thing about deadlines; they don't make things any easier or faster to implement. No matter the deadline, you still have the same amount of work to do.
If your deadline is fixed, something else has to give; either quality or number of features. The Project Triangle sayeth so.
Give up on features and the product might not be what you imagined. Give up quality and you'll pay for it later - with interests.
I have yet to meet an arbitrary deadline that couldn't be budged in the face of realities. Challenge the deadline before you lose your sleep over it.